The present invention generally relates to a packaging machine with heat sealing device for packaging articles with heat sealing film, and in particular to a packaging machine capable to accommodate different sizes of articles to be packaged.
Package films made of plastics or other heat sealable materials are widely used in packaging a variety of products, such as foods, compact disks for computer software and music and books, to protect the products from being damaged or contaminated. In a packaging process, a package film is placed around an article to be packaged. Edges of the package film is then heated to seal along sides of the article. Thus, an important factor that influences the productivity of a packaging line is the heat sealing operation performed by a packaging machine.
A conventional packaging machine forms an L-shaped sealing line along two adjacent sides of an article to be packaged. In other words, it seals two sides simultaneously. However, the operation of the packaging machine is intermittent. The productivity is limited. Furthermore, articles to be packaged may have variable sizes and shapes. This causes deficiency in final package made by the conventional packaging machine. For example, as shown in FIGS. 11 and 12, due to different thickness (dimension in a vertical direction) of the article to be packaged, a sealing line A or Axe2x80x2 may not be located midway of the thickness of an article B. They may be below (sealing line A) or above (sealing line Axe2x80x2) the middle line. Such a situation may cause certain problems. For example, the sealing line may not be properly formed or the package film be damaged or undesired over-packaging be caused. Eventually, the quality of the products is negatively affected.
In a packaging line, articles to be packaged are usually transported by a conveyor system in a longitudinal direction. One way to accommodate articles of different thickness (vertical dimension) to a particular packaging machine is to change the vertical position of the conveyor belt with respect to the packaging machine. This is, however, difficult and ineffective. Modifying a conveyor system to suit for different articles is also very impractical because the packaging line may sometimes constitute only a part of a complete manufacturing line. Changing the conveyor system for the packaging line may cause serious problem to the other portions of the same manufacturing line.
Another disadvantage associated with the above-discussed conventional packaging machine is that the L-shaped sealing line formed by the packaging machine is subject to limitation of size of the particular packaging machine. For articles having elongate lateral side dimension, it is difficult to package the articles with regular packaging machines that forms L-shaped sealing lines.
Accordingly, an object of the present invention is to provide a packaging machine comprising a sealing line adjusting device for adjusting the sealing line with respect to the size of an article to be packaged.
Another object of the present invention is to provide a packaging machine comprising a side sealing device for continuously forming sealing lines along sides of articles.
A further object of the present invention is to provide a packaging machine comprising a side sealing device for forming a side sealing line without causing damage to the package or the package film.
A still further object of the present invention is to provide a packaging machine comprising a side sealing device for forming a continuous side sealing line of unlimited length.
To achieve the above objects, in accordance with the present invention, there is provided a packaging machine for packaging an article having a lateral side along which a sealing line is formed by heat sealing operation. The packaging machine comprises a machine frame having transversely-extending rails on which a conveyor for carrying the article and a package film for packaging the article is movably supported whereby the conveyor and thus the article and the package film are transversely position-adjustable. A side sealing device comprises a film forwarding device for synchronously moving the package film with the article in a longitudinal direction. A position-adjusting device comprises a support structure attached to the conveyor to be transversely position-adjustable. A movable chassis is movably coupled to the support structure by means of a screw rod whereby rotation of the screw rod moves the chassis with respect to the support structure in a vertical direction. A heat sealing blade is supported on the chassis by an actuation device to be reciprocally movable between an extending position for performing heat sealing operation on an edge of the package film along the side of the article to form the sealing line and a retracted position. The heat sealing blade is movable with the chassis for adjusting the position with respect to the article in the vertical direction.